Proper motion determination of open clusters based on the UCAC2 catalogue
We present the kinematics of hundreds of open clusters, based on theUCAC2 Catalogue positions and proper motions. Membership probabilitieswere obtained for the stars in the cluster fields by applying astatistical method uses stellar proper motions. All open clusters withknown distance were investigated, and for 75 clusters this is the firstdetermination of the mean proper motion. The results, including the DSSimages of the cluster's fields with the kinematic members marked, areincorporated in the Open Clusters Catalogue supported on line by ourgroup.
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Proper motions of open clusters based on the TYCHO2 Catalogue. II. Clusters farther than 1 kpc
We determined the mean absolute proper motion of 94 open clusterssituated farther than 1 kpc from the Sun. The results are derived fromthe stellar proper motion data given in the Tycho2 Catalogue. The meanproper motion of the clusters and membership probability of individualstars were obtained from the proper motion data by applying thestatistical method proposed by Sanders (\cite{Sanders1971}). Themeasurements made use of a large number of stars, usually several tens,for each cluster. The total number of stars investigated in the fieldsof the clusters is 4864 of which 2021 were considered members. For 55clusters, this is the first determination of the proper motion. Based onobservations of the ESA Hipparcos satellite. Tables 1 to 95 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/388/168
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On the Precursor Star of the Pulsar in the Crab Nebula
The spatial distribution of the youngest pulsars, with a characteristicage of less than 12,000 years, is considered. All the pulsars except forthe pulsar in the Crab Nebula lie in groups of young OB stars. It issuggested that the precursor of the Crab pulsar was a rapidly rotating,massive OB star. The group of young massive stars from which thefast-moving star was ejected is indicated. Estimates of the age of theprecursor of the Crab pulsar and of the age of the group of young starsfrom which it was ejected favor this hypothesis. It is concluded thatthe fast-moving star must have acquired a high velocity due to thedynamical evolution of the young stellar group.
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Schmidt plate survey in the Galactic centre and anticentre direction. Luminosity and mass functions of open clusters
The proper motions and stellar magnitudes for more than 20 000 starsdistributed in areas around eight open clusters in the directions of theSagittarius-Carina and Perseus spiral arms were used to determine thecluster membership. Both spatial-kinematical and statistical criteriawere used for member selection. The luminosity functions of clustermembers were constructed and used for the further data improvement. Thesafest portions of the luminosity function free both from evolved starsand faint field star contamination were used for mass functionconstruction. The composite mass function was derived from the data onfive young clusters with log t < 8.2. A dependence of the massfunction slope on the adopted input parameters (mass-luminosity relationand distance scale) and on member selection procedure was tested. Theslope was found to vary in a range from 1.36 to 1.80 for lg {calM/M}_sun between 0.3 and 1.2. A possible relation between the individualMF slopes and cluster ages was indicated. The results are in goodagreement with published data.
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Schmidt survey in the Galactic anticentre direction. 1. Investigation of open clusters
A study of four open clusters in the direction of the Galacticanticentre (l = 186(deg) , b = +2(deg) ) is presented. In a field of8.32 square degrees proper motions and B magnitudes for about 79000stars down to 19.5 were determined on Tautenburg Schmidt plates. Formore than 15500 of them U magnitudes down to 17.3 could be obtained.Additionally, OCA Schmidt plates were used to determine V, R magnitudesin a larger field of 24.45 square degrees for 271000 stars down to V =18.2. For stars brighter than V = 15.5 an accuracy of about 1.5 mas/yrhas been estimated for proper motions. The rms errors of stellarmagnitudes and colour indices are 0.09 - 0.12 mag. Several open clustershave been already known in this direction of the sky, e.g. NGC 2168 or M35 (C 0605+243), NGC 2158 (C 0604+241) and IC 2157 (C 0601+240).Inspecting the plates and analysing the colour-magnitude diagrams andpublished data, we could identify an additional anonymous cluster C0605+242 with a projection on the sky near the centre of M 35 but at alarger distance from the Sun. The cluster membership determination wascarried out using information on spatial and proper motion distributionsof stars in the field. The colour-magnitude diagrams were derived downto the limiting stellar magnitude. For each cluster the interstellarextinction A_V, the diameters of the core and corona, the ages andspatial velocity components (V, W) relative to the LSR in the Y, Z -Galactic directions were determined. The distances to the clusters of960 pc, 2600 pc, 2520 pc and 3700 pc were obtained for M 35, IC 2157, C0605+242 and NGC 2158. They show the loci of the clusters in the Localand Perseus spiral arms and at external border of Perseus arm,respectively.
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Estimates of geometric and dynamic parameters of star-gas complexes in the Galaxy
Parameters of geometric models of 11 gas-star complexes (GSCs) wereobtained. We used information about GSC projections onto the celestialsphere and the Galactic plane and about GSC extension along the line ofsight. GSCs were represented as triaxial ellipsoids. To estimate thesemiminor axis of the GSC ellipsoidal model and GSC slope angle to theGalactic plane, we used data on spatial location of open stellarclusters (OSCs) entering GSCs. GSC slopes to the Galactic plane varybetween 2.5 and 20.5 deg. Their semiminor axes are between 11 and 164pc. GSC total masses are estimated from GSC tidal effect on OSCs thatare members of the corresponding GSCs. The effect manifests itself insmaller sizes of young OSCs as compared to their tidal sizes in theforce field of the Galaxy. We used studies of stability of an OSC movingin the joint force field of the Galaxy and spheroidal stationary GSC, aswell as studies of evolution of a virialized cluster located at thecenter of a nonstationary ellipsoidal GSC. Estimated total masses fordifferent GSCs lie between 0.65 x 10 exp 5 solar masses and 11.5 x 10exp 7 solar masses.
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Anatomy of the Gemini OB1 molecular cloud complex
We have investigated the large-scale morphology and properties of themolecular gas in the Gem OB1 cloud complex by mapping over 32 sq deg(177 pc x 221 pc) of the complex in (12)CO(J = 1-0) and (13)CO(J = 1-0)at 50 arcsec sampling with QUARRY on the FCRAO 14 m telescope. The moststriking characteristic of the molecular line images are the series ofarc- and ring-shaped structures found on spatial scales from a fewparsecs in diameter up to at least 35 pc. The morphology and in someinstances the kinematics suggest that these features represent swept-upmolecular material, most likely from expanding H II regions and windblown bubbles. The kinetic temperatures and column densities of themolecular gas were derived from the (12)CO and (13)CO data using theLocal Thermodynamic Equilibrium (LTE) analysis. Most of the moleculargas was found to have kinetic temperatures of less than or approximatelyequal to 10 K, and 50% of the mass of gas is contained in lines of sightwith H2 column densities less than or approximately equal to 2 x1021/sq cm. It was found that only 10% of the molecular massis contained in lines of sight with column densities in excess of1022/sq cm, and that these regions are found almostexclusively near the massive star forming regions within the arcs andrings of molecular gas. The average H2 densities in areas with (13)COemission are between 65-120/cu cm, consistent with previous studies ofcloud complexes, and is independent of whether the regions containsmassive star formation or not. For the Gem OB1 complex as a whole, theaverage H 2 density is 1.2/cu cm, which is only a few time the averageatomic hydrogen density in the interstellar medium. We suggest anoverall picture for the Gem OB1 complex in which most of the moleculargas is contained in relatively cold, low column density molecularmaterial. The high column density regions in the Gem OB1 complex formthrough the external compression of the molecular gas by the winds and HII regions from newly formed massive stars. Thus once massive starrformation is initiated, the structure and further evolution of the cloudcomplex is largely a result of the interactions of expanding H IIregions and stellar winds with the ambient molecular material.
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Catalogue of blue stragglers in open clusters.
An extensive survey of blue straggler candidates in galactic openclusters of both hemispheres is presented. The blue stragglers wereselected considering their positions in the cluster colour-magnitudediagrams.They were categorized according to the accuracy of thephotometric measurements and membership probabilities. An amount of 959blue straggler candidates in 390 open clusters of all ages wereidentified and classified. A set of basic data is given for everycluster and blue straggler. The information is arranged in the form of acatalogue. Blue stragglers are found in clusters of all ages. Thepercentage of clusters with blue stragglers generally grows with age andrichness of the clusters. The mean ratio of the number of bluestragglers to the number of cluster main sequence stars is approximatelyconstant up to a cluster age of about 10^8.6^ yr and rises for olderclusters. In general, the blue stragglers show a remarkable degree ofcentral concentration.
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Integrated photometric properties of open clusters
Galactic open clusters provide an abundant sample of stellar aggregatesof various sizes, ages and metal abundances, apt to constitute atemplate for comparison with star systems in other galaxies. In thispaper we present and discuss a standard methodology to synthesize U,B,Vfluxes and colours, and apply it to a set of 138 open clusters. Resultsare compared with previous ones available in the literature. We wereable to calibrate a mass-luminosity relation by which we evaluated themass of ~400 open clusters, leading to a well defined present-day massfunction. The number-complete sample of galactic open clusters presentedin Battinelli & Capuzzo-Dolcetta (1991) is enlarged of a 15%.
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Formation and evolutionary properties of the Galactic open cluster system
Results are reported from a statistical analysis of observational dataon 100 open clusters within 2 kpc of the sun, selected from the catalogof Lynga (1987). The selection criteria and the completeness of thesample are discussed; the data are compiled in a table; and the analysisresults are presented in a series of graphs and characterized in detail.A cluster formation rate of 0.45 clusters/kpc Myr is found,significantly lower than the rates determined previously (using clusterswithin 1 kpc of the sun) and corresponding to a cluster star-formationefficiency of 0.0063. The low average cluster lifetime (about 10 Myr)suggests that clusters are formed as unstable systems.
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Deep-sky wonders.
Not Available
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Young stellar-gas complexes in the Galaxy
It is found that about 90 percent of OB-associations and o-b2 clusterssituated within 3 kpc of the sun can be united into complexes withdiameters of 150-700 pc. Almost all of these clusters contain giantmolecular clouds with a mass greater than about 100,000 solar masses. Anumber of complexes are associated with giant H I clouds; a few of thesmall complexes are situated in the HI caverns. The concentration ofOB-associations and young clusters in star complexes attests to theircommon origin in the supergiant gaseous clouds.
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Catalog of open clusters and associated interstellar matter.
Not Available
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A cluster analysis of young open clusters
Cluster analysis methods are used to consider the galactic distributionof 224 open clusters with an age up to 10 to the 8th yrs. Most of theseclusters enter condensations with characteristic dimensions of a fewhundred parsecs. Some condensations are so similar in terms of the age,integrated color, and radial velocity of their components, that thiscannot be considered a coincidence. This suggests that each condensationis a physical entity consisting of clusters apparently linked by acommon origin.
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Catalogue of UBV Photometry and MK Spectral Types in Open Clusters (Third Edition)
Not Available
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Open clusters and galactic structure
A total of 610 references to 434 clusters are employed in thecompilation of a catalog of open clusters with color-magnitude diagramson the UBV or RGU systems. Estimates of reddening, distance modulus, ageand number of cluster members are included. Although the sample isconsidered representative of the discoverable clusters in the galaxy,the observed distribution is nonuniform because of interstellarobscuration. Cluster distribution in the galactic plane is found to bedominated by the locations of dust clouds rather than by spiralstructure. The distributions of clusters as a function of age andrichness class show that the lifetimes of poor clusters are much shorterthan rich ones, and that clusters in the outer disk survive longer thanthose in the inner disk. An outer disk age which is only about 50% theage of the globular clusters is indicated by cluster statistics. Thethickening of the galactic disk with increasing galactocentric distancemay be due to either a younger dynamical age or a lower gravitationalpotential in the outer regions.
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A photometry study of the open cluster IC 2157
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&AS...11..287G
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A catalogue of galactic star clusters observed in three colours
Abstract image available at:http://adsabs.harvard.edu/abs/1971A&AS....4..241B
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Die räumliche Verteilung von 156 galaktischen Sternhaufen in Abhängigkeit von ihrem Alter. Mit 7 Textabbildungen
Not Available
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Farben-Helligkeits-Diagramme und Entfernungen von 10 offenen Sternhaufen. Mit 10 Textabbildungen
Not Available
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Red indices in galactic clusters. II.Messier 35, NGC 2158, IC 2157, NGC 2129, 1817, 2266, 2281
Not Available
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